The present invention relates to cast tiles, particularly cast ceiling tiles which are manufactured by a process which requires particular rheological properties of the paste from which the tile is made. The paste is essentially made up of a binder and filler. Normally, to acquire the proper rheological properties, the paste contains starch as the binder. The rheological properties of the paste are necessary because during the manufacture of the cast ceiling tile, the compound breaks down under the shear of an oscillating bar which imparts a unique surface to the cast ceiling tile.
Unfortunately, starch requires long, costly drying cycles and is hydroscopic, therefore, the finished cast ceiling tiles absorb moisture. The absorbed moisture causes sagging and warping of the installed cast ceiling tiles. A desirable binder would therefore have the proper rheological properties when combined with mineral wool and the filler and at the same time would not require long drying cycles and would not be as hydroscopic as starch. Accordingly, the present invention is such a binder for cast ceiling tile.